I mean, you take one look at Greek statues and Roman busts and you realize that people figured how to aim for realism, at least when it came to the human body and faces, over 2000 years ago.
Yet, unlike sculpture, paintings and drawings remained, uh, “immature” for centuries afterwards (to my limited knowledge, it was the Italian Renaissance that started making realistic paintings). Why?
Also the time needed to perfect that skill wouldn’t have been available that far back. If you’re needing to spend the bulk of your time hunting/gathering food and other forms of basic survival I don’t think you’d have the hours every evening to work on your shading techniques.
Excellent point, as others have astutely pointed out, a love of the arts is often cultural, and most artists need essentially a set of people who love their art and buy it or they will be a “starving artist.” So you also need a society that appreciates art enough to let certain people have all that time.